1. Field of the Invention
The present invention relates to a memory module. In particular, the present invention relates to a memory module which is mounted with a control semiconductor package, for example, an AMB (Advanced Memory Buffer) package and the like, and supports high speeds and large capacities in the field of memory modules which are utilized as main memories for personal computers, servers, workstations and the like. This type of memory is suitable, for example, for FB-DIMM (Fully Buffered Dual-In-Line Memory).
2. Description of the Related Art
As a conventional memory module, there is one shown in JP-A-11-354701. The memory module disclosed in this official gazette has a removable cover-like heat sink (radiator) mounted on a module board on which memory IC's such as DRAM are mounted along both sides, in order to dissipate heat generated from the memory IC's. The heat sink is made of a flexible material and has an inverted C-shape in cross section in the mounting direction to the board. The inner surface of the inverted C-shape is kept in contact with the memory IC's through a highly thermally conductive member such as highly thermally conductive rubber, and multiple asperities are formed on the outer surface of the inverted C-shape.
Recently, FB-DIMM has been proposed for a memory module for a server system which is required to provide high speeds and large capacity. The FB-DIMM has a plurality of semiconductor memory packages (DRAM packages) arranged and mounted on a module board, and a control semiconductor package (AMB package) disposed in a central region of the semiconductor memory package array.
In such a FB-DIMM, the control semiconductor package, which generates a larger amount of heat than the semiconductor memory packages, is mounted in the central region where there is the arrangement of a plurality of semiconductor memory packages, so that there is concern for a temperature rise in the semiconductor memory packages mounted near the control semiconductor package. Therefore, it is contemplated to use one radiator, in a manner similar to the conventional example which uses one radiator, and dispose this radiator over both the control semiconductor package and semiconductor memory packages. In this event, however, there is a concern that the semiconductor packages are affected by high temperatures of the control semiconductor package, resulting in failure to produce a cooling effect, though the temperature of the entire module is leveled out. In particular, when a control semiconductor package is used which exhibits a heatproof temperature that is higher than the allowable heatproof temperature of semiconductor memory packages, a problem is highly likely to arise in regard to the reliability of the semiconductor memory packages.